Varroa Mites 2: Powdered Sugar Roll

A powdered sugar roll is a great way to estimate how many mites are in a honeybee colony. Knowing the mite load can help beekeepers more sustainably manage varroa mite load in bees. We prefer this method to the alcohol wash as the bees will survive this process.

In this post, we’ll show you how to make a sugar roll test kit, explain how to do the sugar roll, and then describe some management scenarios using the results.

Basically, the bees take a roll in the powdered sugar to knock off any mites attached. Then shake the mites and sugar onto a paper plate and spray with water to see the brown mites.

Sugar Roll Kit

We put together this kit to make it easy to grab and head out to the bee yard.

White paper plate (not shown). Needs to be wax-coated so it is water-resistant.

Storage container. We used a 6.5 quart Hefty container. One with curved sides works best. You will need to scoop 1/2 cup of bees from this container.

Mason Jar with ring. We use a wide-mouthed pint or half-pint jar.

Metal screen. This can be tricky to find. We used #8 hardware cloth, cut to fit tightly in the ring. Some lumbar yards sell hardware cloth by the foot, but most won’t. You’d have to buy the entire roll.

Other sources for metal screen include some car air filters, office supplies made from screened metal, thrift stores, vegetable or juice screens, or screen from the bottom of a sieve. Screen needs to have squares smaller than 1/4 inch. Window screen holes are too small.

#5 hardware cloth is too big.

Method

Remove a frame of bees from the hive. Shake the bees from the frame into the storage container. Quickly scoop 1/2 cup of bees from the container and place them in the mason jar. Add 1T powdered sugar to the jar and roll the jar to coat the bees. Let it sit at least 1 minute. This minute is essential as it will give enough time for mites to drop off of the bees.

Shake the contents onto a white paper plate. The bees will stay in the jar and the powdered sugar and 95% of the mites will fall out onto the paper plate. Lightly spray the powdered sugar with water. This will reveal the mites, which are brown specks on the plate. Count the number of mites on the plate. Put the powdered sugar-y bees back in the hive.

Here are two videos on doing a powdered sugar roll.

Calculations and example

Take the number of mites and divide by 3. This will give you the number of mites per 100 bees. Then multiply the number by 2 to account for the mites that are hidden in the brood chamber. (About half of mites are in the brood chamber and half are on the adult bees.)

Example:

Say I found 30 mites in the 1/2 cup sample.

Then 30 / 3 = 10. 10 x 2 = 20.

Then approximately 20% of bees in the hive have mites.

Our mite threshold is about 5-6%. If it is above 5-6%, we may decide to treat for mites. If below, we ignore the mites and do not treat.

Treatment Decision Examples

1. If 7% of bees in the hive have mites in the spring, it may be a good idea to treat the hive for mites. Mite load will increase through the summer.

2. If 2% of bees have mites in the spring, wait to treat. Sample again in fall.

3. If 7% of bees have mites in the fall, wait to treat. The mite load will decrease over the winter as mites require brood to reproduce. Test again in the spring.

4. If 30% of bees have mites in the fall, it may be a good idea to treat for mites.